The present invention relates to a head holder on which a head of a subject is mounted, as well as an imaging table and an X-ray CT (Computed Tomography) apparatus having such a head holder.
In recent X-ray CT apparatuses, the scanning gantry without a tilt mechanism has been developed. There are principal reasons for it such as to improve rigidity of a frame to cope with a faster rotational speed of the scanning gantry, an angle range in which the scanning gantry can be tilted being restricted due to an increase in the number of rows of X-ray detector elements, and to reduce the manufacturing cost by eliminating the tilt mechanism.
When obtaining an image of a subject's head using a scanning gantry without a tilt mechanism, a slice axis of a tomogram is aligned with an axis of a head portion. Also, it might be necessary to prevent crystalline lenses, which are highly sensitive to radiation, from being too much exposed. In order to do so, there is a case where it is desired to incline the head portion with respect to an imaging table to form a certain angle.
In view of the above, there is proposed a head holder whose tilt angle of a portion on which a head is mounted can be varied (see for example, Japanese Patent No. 4603712, Japanese Unexamined Patent Publication No. 299059/1995, and Japanese Unexamined Patent Publication No. 75333/1997).
A head holder disclosed in Japanese Patent No. 4603712 is configured such that a portion on which a head is mounted is slidable along a curved surface of a base supporting the portion. Therefore, when a subject is laid on an imaging table and a tilt angle of the head holder is adjusted, an operator such as an imaging engineer has to lift and support the head of the subject and to move the head holder, exhibiting poor workability. Further, when the head holder is slid, a position of a recessed portion on which the head is placed varies. Besides, the way the position varies does not coincide with the way the head portion moves. Therefore, when the tilt angle is adjusted, the subject has to adjust the position by moving his or her body.
Also, a head holder disclosed in Japanese Unexamined Patent Publication No. 299059/1995, and Japanese Unexamined Patent Publication No. 75333/1997 is configured such that a portion on which a head is placed can swing or rotate, but its structure is complicated. In particular, a mechanism to fix the portion on which the head is placed is complicated, causing poor workability in adjustment of the tilt angle.
With such circumstances, improvement in workability of adjusting the tilt angle of the head holder is desired.